JP4591155B2 - Exposure method and apparatus, and device manufacturing method - Google Patents

Description

  The present invention relates to an exposure technique for transferring a plurality of patterns arranged in a lattice shape onto an object via a projection optical system. For example, a contact hole pattern arranged in a lattice shape is placed on an object such as a wafer. It is suitable for use in a device manufacturing process for transferring.

  For example, in a lithography process, which is one of the manufacturing processes of semiconductor devices, a pattern formed on a mask such as a reticle or photomask is transferred and exposed onto a wafer (or a glass plate or the like) coated with a resist as a photoreceptor. In order to do so, an exposure apparatus is used. As the exposure apparatus, a batch exposure type (stationary exposure type) projection exposure apparatus such as a stepper or a scanning exposure type projection exposure apparatus (scanning type exposure apparatus) such as a scanning stepper is used.

In these exposure apparatuses, the numerical aperture of the projection optical system is gradually increased to increase the resolution, and the exposure wavelength is gradually shortened. At present, excimer laser light sources such as KrF excimer laser (wavelength 248 nm) and ArF excimer laser (wavelength 193 nm) are mainly used as exposure light sources. However, if the exposure wavelength is shortened simply by increasing the numerical aperture, the depth of focus of the projection optical system may become narrower than the allowable range. Therefore, as an exposure method capable of increasing the resolution while ensuring a predetermined depth of focus, an exposure method using a phase shift mask (see, for example, Patent Document 1), a modified illumination method using annular illumination, and the like have been proposed. ing.
Japanese Examined Patent Publication No. 62-50811

  One of the processes requiring high resolution in the manufacturing process of a semiconductor device is a process of forming contact holes, which are a plurality of fine opening patterns arranged in a lattice pattern, on a wafer. Among the contact hole patterns, there is a one-way dense pattern that is isolated in one direction and periodically arranged at a fine pitch in a direction perpendicular thereto. In the process of exposing such a one-way dense pattern, conventionally, an exposure method using a modified illumination method such as dipole illumination has been used in order to increase the resolution while ensuring the depth of focus.

Recently, the degree of integration of devices is further improved, and the arrangement pitch of contact holes is also becoming finer. However, when the arrangement pitch of the unidirectional dense contact hole pattern is reduced, there is a problem that a sufficient depth of focus cannot be ensured only by using the modified illumination method.
In view of the above, the present invention provides an exposure technique and a device manufacturing technique that can obtain a high resolution and ensure a wide depth of focus when transferring a plurality of patterns arranged in a lattice like a one-way dense pattern. The purpose is to do.

  The exposure method according to the present invention is an exposure method in which a plurality of patterns (31) arranged in a lattice shape are transferred and exposed onto an object via a projection optical system (PL), and exposure from an illumination optical system (2-9) is performed. When illuminating a plurality of the patterns with a beam, two first regions (23A, 23B; 24A, 24B) shifted substantially symmetrically from the optical axis on the pupil plane of the illumination optical system, and the two first regions The amount of light of the exposure beam in the two second regions (23C, 23D; 24C, 24D) that are substantially symmetrically shifted with respect to the optical axis inside the light source, and the polarization of the exposure beam And a step of setting the state to linearly polarized light in which the polarization directions of the two first regions and the two second regions are substantially orthogonal to each other on the pupil plane of the illumination optical system.

According to the present invention, it is possible to expose the images of the plurality of patterns with high resolution by applying the modified illumination. Furthermore, by controlling the polarization state of the exposure beam, a wide depth of focus can be secured when the plurality of patterns are isolated in one direction and periodic in a direction perpendicular thereto.
In the present invention, when projecting a plurality of images of the pattern onto the object via the projection optical system, a step of relatively moving the pattern image and the object in the optical axis direction of the projection optical system. Further, it may be provided. This may further increase the depth of focus.

As an example, each of the two first regions and the second region on the pupil plane of the illumination optical system is arranged along a straight line (25A; 25B) substantially passing through the optical axis, and the two first regions. The polarization direction of the exposure beam in the region may be a direction orthogonal to the straight line, and the polarization direction of the exposure beam in the two second regions may be a direction parallel to the straight line.
In this case, the plurality of patterns may be arranged periodically in a direction corresponding to a direction parallel to the straight line and may be substantially isolated in a direction corresponding to a direction orthogonal to the straight line. At this time, the resolution and depth of focus in the periodic direction are improved by the linearly polarized exposure beams from the two first regions, and the resolution in the isolated direction is improved by the linearly polarized exposure beams from the second region. And the depth of focus is improved.

As an example, the coherence factor outside the two first regions is 0.8 to 0.95, and the distance between the center of the two second regions and the optical axis is 0 in terms of the coherence factor. The second region is a circular region having a radius of 0.05 to 0.2 in terms of a coherence factor.
Next, the exposure apparatus according to the present invention illuminates the predetermined pattern (R) with the exposure beam from the illumination optical system (2-9), and displays the object (W) as an image through the projection optical system (PL) of the predetermined pattern. ) In the exposure apparatus that exposes the light on the pupil plane of the illumination optical system according to the arrangement of the plurality of patterns when the predetermined pattern includes a plurality of patterns (31) arranged in a grid pattern. Two first regions (23A, 23B; 24A, 24B) that are substantially symmetrically displaced from the axis, and two second regions (23C, 23A, 24B) that are substantially symmetrically displaced with respect to the optical axis inside the two first regions. , 23D; 24C, 24D) and the exposure beam in the illumination optical system on the pupil plane of the illumination optical system by increasing the amount of light of the exposure beam in other areas. The polarization direction is substantially the same with the second region Those with the illumination condition control system that sets the linearly polarized light (12～16,60～63) perpendicular to.

According to the present invention, the images of the plurality of patterns can be exposed with high resolution by applying modified illumination. Further, by controlling the polarization state of the exposure beam, a wide depth of focus can be secured when the plurality of patterns are isolated in one direction and periodic in a direction perpendicular thereto.
In the present invention, a moving device (38) for relatively moving the image of the predetermined pattern and the object in the optical axis direction of the projection optical system may be further provided. The depth of focus may be further improved by relatively moving the image of the predetermined pattern and the object in the direction of the optical axis using the moving device.

  As an example, each of the two first and second regions on the pupil plane of the illumination optical system is arranged along a straight line (25A; 25B) substantially passing through the optical axis, and the illumination condition control is performed. The system may have the polarization direction of the exposure beam in two first regions as a direction perpendicular to the straight line, and the polarization direction of the exposure beam in two second regions as a direction parallel to the straight line.

  The plurality of patterns may be periodically arranged in a direction corresponding to a direction parallel to the straight line, and may be substantially isolated in a direction corresponding to a direction orthogonal to the straight line. At this time, the resolution and depth of focus are improved in the periodic direction by the exposure beam from the first region, and the resolution and depth of focus are improved in the isolated direction by the exposure beam from the second region.

  Next, the device manufacturing method according to the present invention includes an exposure step of transferring a circuit pattern onto a photoreceptor using the exposure method or exposure apparatus of the present invention. According to the present invention, in the exposure process, when transferring a pattern arranged in a lattice like a one-way dense pattern, a high resolution can be obtained while ensuring a wide depth of focus. Devices with various patterns can be manufactured with a high yield. The device manufacturing method of the present invention can also be applied when manufacturing a flash memory or CPU as an example.

According to the present invention, by combining the modified illumination and the control of the polarization state of the exposure beam, a high resolution can be obtained when transferring a plurality of patterns arranged in a lattice like a one-way dense pattern. A wide depth of focus can be secured.
In addition, the depth of focus may be further improved by relatively moving the image of the pattern and the object in the optical axis direction of the projection optical system during exposure.

A preferred first embodiment of the present invention will be described below with reference to FIGS. In this example, the present invention is applied when a pattern for contact holes arranged in a lattice pattern is transferred.
FIG. 1 is a diagram schematically showing the configuration of the exposure apparatus of this example. In FIG. 1, the Z axis along the normal direction of the surface (wafer surface) of a wafer W coated with a photoresist, which is a photosensitive substrate (photoreceptor), in the plane parallel to the wafer surface in FIG. The Y axis is set in a direction parallel to the X axis, and the X axis is set in a direction perpendicular to the paper surface of FIG.

The exposure apparatus of this embodiment includes a laser light source 1 for supplying illumination light (exposure light) as an exposure beam. In this example, an ArF excimer laser light source that supplies light with a wavelength of 193 nm is used as the laser light source 1 (exposure light source). However, for example, a KrF excimer laser light source that supplies light with a wavelength of 248 nm, an F ₂ laser light source (wavelength) 157 nm), or a harmonic generator of a YAG laser or a solid-state laser (such as a semiconductor laser) can also be used.

  A substantially parallel light beam emitted from the laser light source 1 along the Z direction has a rectangular cross section extending along the X direction and is incident on a beam expander 2 including a pair of lenses 2a and 2b. Each of the lenses 2a and 2b has a negative refracting power and a positive refracting power in the plane of FIG. 1 (in the YZ plane). Accordingly, the light beam incident on the beam expander 2 is enlarged in the plane of FIG. 1 and shaped into a light beam having a predetermined rectangular cross section. The substantially parallel light beam via the beam expander 2 as the shaping optical system is deflected in the Y direction by the bending mirror 3, and then passes through the phase member 10, the depolarizer (depolarizing element) 20, and the diffractive optical element 4. Then, the light enters the afocal zoom lens 5. The configurations and operations of the phase member 10 and the depolarizer 20 will be described later. In general, a diffractive optical element is formed by forming a step having a pitch that is about the wavelength of light incident on a substrate, and has an action of diffracting an incident beam to a desired angle. Specifically, the diffractive optical element 4 has a function of forming a circular light intensity distribution in the far field (or Fraunhofer diffraction region) when a parallel light beam having a rectangular cross section is incident.

  Therefore, the light beam emitted from the diffractive optical element 4 forms a circular light intensity distribution at the pupil position of the afocal zoom lens 5, that is, a light beam having a circular cross section. The diffractive optical element 4 is configured to be retractable from the illumination optical path. The afocal zoom lens 5 is configured so that the magnification can be continuously changed within a predetermined range while maintaining an afocal system (non-focal optical system). The light beam that has passed through the afocal zoom lens 5 enters the diffractive optical element 6 for annular illumination. The afocal zoom lens 5 optically substantially conjugates the divergence origin of the diffractive optical element 4 and the diffractive surface of the diffractive optical element 6. Then, the number of entrances of the light beam condensed on one point of the diffractive surface of the diffractive optical element 6 or a surface in the vicinity thereof changes depending on the magnification of the afocal zoom lens 5.

  The diffractive optical element 6 for annular illumination has a function of forming a ring-shaped light intensity distribution in the far field when a parallel light beam is incident. The diffractive optical element 6 is configured to be detachable with respect to the illumination optical path, and includes a row of diffractive optical elements 60 and 61 for quadrupole illumination, a diffractive optical element 62 for ordinary quadrupole illumination, and normal illumination described later. The diffractive optical element 63 can be switched.

  The light beam emitted from the diffractive optical element 6 enters the zoom lens 7 along the optical axis AX of the illumination optical system. In the vicinity of the rear focal plane of the zoom lens 7, the incident surface of the microlens array (or fly-eye lens) 8 is positioned. The microlens array 8 is an optical element made up of a large number of microlenses having positive refracting power that are arranged vertically and horizontally and densely. In general, a microlens array is configured by forming a group of microlenses by performing an etching process on a plane parallel plate, for example.

  Here, each minute lens constituting the microlens array 8 is smaller than each lens element constituting the fly-eye lens. Further, unlike the fly-eye lens composed of lens elements isolated from each other, the microlens array 8 is formed integrally with a large number of microlenses (microrefractive surfaces) without being isolated from each other. However, the microlens array 8 is the same wavefront division type optical integrator as the fly-eye lens in that lens elements having positive refractive power are arranged vertically and horizontally.

  As described above, the luminous flux from the circular light intensity distribution formed at the pupil position of the afocal zoom lens 5 via the diffractive optical element 4 is emitted from the afocal zoom lens 5 and then has various angular components. Is incident on the diffractive optical element 6. That is, the diffractive optical element 4 constitutes an optical integrator having an angular light beam forming function. On the other hand, the diffractive optical element 6 has a function as a light beam conversion element that forms a ring-shaped light intensity distribution in the far field when a parallel light beam is incident. Therefore, the light beam emitted from the diffractive optical element 6 forms an illuminating field that is, for example, an optical field centered on the optical axis AX on the rear focal plane of the zoom lens 7 (and hence on the incident surface of the microlens array 8). .

  The outer diameter of the zonal illumination field formed on the incident surface of the microlens array 8 changes depending on the focal length of the zoom lens 7. Thus, the zoom lens 7 substantially connects the diffractive optical element 6 and the incident surface of the microlens array 8 in a Fourier transform relationship. The light beam incident on the microlens array 8 is two-dimensionally divided and is incident on the pupil plane (hereinafter referred to as “illumination system pupil plane”) PIL of the illumination optical system, which is the rear focal plane of the microlens array 8. A large number of annular light sources (hereinafter referred to as “secondary light sources”) that are the same as the illumination field formed by the luminous flux are formed. The secondary light source can be regarded as a region having a larger amount of illumination light than other regions, and when the secondary light source includes a region eccentric from the optical axis AX, such as a ring zone region or a quadrupole region, The illumination condition is modified illumination.

  In FIG. 1, a light beam from an annular secondary light source formed on the rear focal plane (illumination system pupil plane PIL) of the microlens array 8 is subjected to a condensing action of the condenser optical system 9, and is then given a predetermined amount. A mask M made of a reticle or a photomask on which a pattern is formed is illuminated in a superimposed manner. A field stop (not shown) is disposed in the vicinity of the pattern surface (lower surface) of the mask M. It is also possible to form an image once in the condenser optical system 9 and arrange a field stop in the vicinity of the image formation surface. In this example, the illumination optical system is configured to include optical members from the beam expander 2 to the condenser optical system 9.

  The light beam that has passed through the pattern of the mask M forms an image of the mask pattern on the wafer W coated with a photoresist, which is a photosensitive substrate (photoconductor), via the projection optical system PL of the optical axis AX1. If the size of one shot area on the wafer W is 33 mm square and the magnification of the projection optical system PL is 1/4, the size of the pattern formation area of the mask M is 132 (= 33 × 4) mm square. . The pupil PPL of the projection optical system PL (region corresponding to the numerical aperture NA on the image side of the projection optical system PL) is defined by an aperture stop (not shown). The position of the pupil PPL of the projection optical system PL and the illumination system pupil plane PIL are conjugate. Then, by performing batch exposure or scan exposure while driving and controlling the wafer W two-dimensionally in a plane (XY plane) orthogonal to the optical axis AX1 of the projection optical system PL, each shot area (partition area) of the wafer W is performed. ) Is sequentially exposed with the pattern image of the mask M.

  In the present embodiment, when the diffractive optical element 6 is disposed in the illumination optical path, if the magnification of the afocal zoom lens 5 changes, the center height of the annular secondary light source (the optical axis AX of the center line of the annular zone) Without changing the distance), only its width (1/2 of the difference between the outer diameter and the inner diameter) changes. That is, by changing the magnification of the afocal zoom lens 5, both the size (outer diameter) and the shape (annular ratio = inner diameter / outer diameter) of the annular light source can be changed.

  When the focal length of the zoom lens 7 is changed, the center height and the width thereof are both changed without changing the annular ratio of the annular secondary light source. That is, by changing the focal length of the zoom lens 7, the outer diameter can be changed without changing the ring zone ratio of the secondary illuminating light source. As described above, in the present embodiment, by appropriately changing the magnification of the afocal zoom lens 5 and the focal length of the zoom lens 7, only the annular ratio is changed without changing the outer diameter of the annular secondary light source. Can be changed.

  Note that a single row of quadrupole illumination can be performed by setting the diffractive optical element 60 in the illumination optical path instead of the diffractive optical element 6. The diffractive optical element 60 has a function of forming a four-point light intensity distribution in the far field when a parallel light beam is incident. Therefore, the light beam that has passed through the diffractive optical element 60 forms, for example, four illumination fields (four-polar illumination fields) along a straight line passing through the optical axis AX on the incident surface of the microlens array 8. Accordingly, as shown in FIG. 2A, a quadrupolar secondary light source is formed on the rear focal plane (illumination system pupil plane PIL) of the microlens array 8.

  In the illumination system pupil plane PIL of FIG. 2A, two secondary light sources 23A and 23B (first region) elongated in the Z direction and symmetrically arranged so as to sandwich the optical axis AX in the X direction, In the two circular secondary light sources 23C and 23D (second region) arranged symmetrically so as to sandwich the optical axis AX in the X direction between the secondary light sources 23A and 23B, the amount of illumination light is It is set to be substantially uniform and large, and the light quantity of illumination light is set to almost zero in other areas. The centers of the secondary light sources 23A, 23C, 23D, and 23B are arranged in a line on a straight line 25A that passes through the optical axis AX and is parallel to the X axis. The X direction and the Z direction on the illumination system pupil plane PIL correspond to the X direction and the Y direction on the mask M in FIG.

  In the quadrupole illumination, as in the case of the annular illumination, the outer diameter of the quadrupolar secondary light source (the two outer secondary light sources 23A and 23B are changed by changing the magnification of the afocal zoom lens 5). It is possible to change both the circumscribed circle diameter Do) and a kind of annular ratio (the value obtained by dividing the diameter Di of the circle inscribed in the two inner secondary light sources 23C and 23D by the diameter Do of the circumscribed circle). . Further, by changing the focal length of the zoom lens 7, the outer diameter of the quadrupolar secondary light sources 23A to 23D can be changed without changing the ring zone ratio. As a result, by appropriately changing the magnification of the afocal zoom lens 5 and the focal length of the zoom lens 7, only one kind of annular ratio is obtained without changing the outer diameter of the quadrupolar secondary light sources 23A to 23D. Can also be changed.

FIG. 3 is an explanatory diagram of the shape of the quadrupolar secondary light sources 23A to 23D in FIG. Here, the numerical aperture NAi of the illumination optical system, together represented using the object side of the projection optical system PL coherence factor (sigma value) is the ratio for the numerical aperture NA _OB of (mask side), the illumination system pupil plane PIL The size and shape of the secondary light source are converted into their coherence factors (σ values) as appropriate. At this time, the σ value of the numerical aperture NAi of the illumination optical system is as follows.

σ = NAi / NA _OB (1)
In FIG. 3, on a straight line 25A passing through the optical axis AX and parallel to the X axis, points 28A and 28B are taken at positions of a distance R5 in the + X direction and the −X direction from the optical axis AX, and the secondary light source 23A is taken from the optical axis AX. And the distance to the center of 23B is R4, the width in the X direction of the secondary light sources 23A and 23B is t, and the width in the Z direction is h. Also, draw a circle 26 and radius of NAi circumference 27 of radius NA _OB around the optical axis AX, the distance from the optical axis AX to two secondary light source 23C and the center of 23D of the inner R3, circular The radius of the secondary light sources 23C and 23D is R2. At this time, as an example, when the circumferences 29A and 29B having a radius NAi with the points 28A and 28B as the center are drawn, two elliptical regions elongated in the Z direction surrounded by the circumference 27 and the circumference 29A (or 29B) are obtained. This is the next light source 23A (or 23B).

Therefore, the distance R5 is twice the distance R4 as follows.
R5 = 2 × R4 (2)
Further, since the radius NAi of the circumference 27 is larger than the distance R4, the following condition is satisfied.
NAi> R4 (3)
t = 2 (NAi-R4) (4)
Further, since the inner secondary light sources 23C and 23D do not overlap the outer secondary light sources 23A and 23B and the inner secondary light sources 23C and 23D are separated from each other, the following conditions are satisfied.

R4-t / 2> R3 + R2 (5)
R3> R2 (6)
In this case, as an example, the radius NAi of the circumference 27 and the circumferences 29A and 29B, that is, the outer radius of the secondary light sources 23A and 23B is set to 0.8 to 0.95 in terms of σ value as follows. The reason why the outer radii of the secondary light sources 23A and 23B are set large in this way is to obtain as high a resolution as possible in the X direction.

0.8NA _OB ≦ NAi ≦ 0.95NA _OB (7)
Further, the distance R5 (twice the distance R4) is set to a distance corresponding to the diffraction angle of the first-order diffracted light in the X direction according to the periodic pattern to be transferred as an example. As a result, when the circumference 26 in FIG. 3 is regarded as the pupil of the projection optical system PL, the first-order diffracted light in the X direction from one secondary light source 23A (or 23B) is the other secondary light source 23B (or 23A). Therefore, the image plane is inclined by the zero-order light from the secondary light source 23A and the image of the first-order diffracted light of the light beam from the secondary light source 23A, and the zero-order light from the secondary light source 23B. And an image formed by adding the first-order diffracted light of the light beam from the secondary light source 23B, a periodic pattern image is formed with a deep focal depth.

Further, the width h in the Z direction of the outer secondary light sources 23A and 23B is about 2 to 4 times the width t in the X direction. In short, it is preferable to set the width h in the Z direction of the secondary light sources 23A and 23B so that the secondary light sources 23A and 23B do not protrude from the circumference 27 having the radius NAi. For this reason, the shape of the secondary light sources 23A and 23B may be an ellipse elongated in the Z direction.
The distance R3 from the center optical axis of the two inner secondary light sources 23C and 23D is set between 0.15 and 0.35 in terms of σ value as follows, and the secondary light source 23C And the radius R2 of 23D is set between 0.05 and 0.2 in terms of σ value. The secondary light sources 23C and 23D can also have a shape other than a circle such as an ellipse.

0.15 NA _OB ≦ R 3 ≦ 0.35 NA _OB (8)
0.05 NA _OB ≦ R 2 ≦ 0.2 NA _OB (9)
In this case, the light beams from the two inner secondary light sources 23C and 23D are mainly used to form an image of an isolated pattern in the Z direction (corresponding to the Y direction on the mask M). At this time, by setting the distance R3 within the range of the equation (8), the periodic pattern image in the X direction is not adversely affected, and the wafer surface from the isolated pattern in the Z direction is applied. Since zeroth-order light incident perpendicularly disappears, the depth of focus of the image of the isolated pattern can be increased. Further, by satisfying the condition of the expression (9) for the radius R2 of the secondary light sources 23C and 23D, the resolution can be improved in the Z direction in the same way as the small σ illumination with respect to the isolated pattern. In this way, by using a single row of quadrupole illumination in the X direction in FIG. 2A, a unidirectional dense pattern that is isolated in the direction corresponding to the Z direction and periodic in the X direction has high resolution and a deep focus. Can be projected in depth.

  In FIG. 1, another row of quadrupole illumination can be performed by setting a diffractive optical element 61 in the illumination optical path instead of the diffractive optical element 6. The diffractive optical element 61 also has a function of forming a four-point light intensity distribution in the far field when a parallel light beam is incident. Accordingly, the light beam that has passed through the diffractive optical element 61 forms, for example, four illumination fields (four-polar illumination fields) along a straight line passing through the optical axis AX on the incident surface of the microlens array 8. Accordingly, as shown in FIG. 2B, a quadrupolar secondary light source is formed on the rear focal plane (illumination system pupil plane PIL) of the microlens array 8.

  In the illumination system pupil plane PIL of FIG. 2B, the secondary light sources 23A to 23D of FIG. 2A are rotated 90 ° counterclockwise and symmetrically 2 so as to sandwich the optical axis AX in the Z direction. Two secondary light sources 24A and 24B (first region) and two secondary light sources 24C and 24D (second region) are arranged, and in these secondary light sources 24A to 24D, the amount of illumination light is substantially uniform. It is set to be large, and the light quantity of illumination light is set to almost zero in other areas. The centers of the secondary light sources 24A to 24D are arranged in a line on a straight line 25B that passes through the optical axis AX and is parallel to the Z axis. By using a single row of quadrupole illumination in the Z direction in FIG. 2B, a unidirectional dense pattern that is isolated in the X direction and periodic in the direction corresponding to the Z direction can be obtained with high resolution and a deep focal depth. Can project.

In this example, when using a single row of quadrupole illumination in FIG. 2A or FIG. 2B, control of the polarization state of illumination light is also used in order to further improve the depth of focus (details will be described later). .
Further, by setting the diffractive optical element 62 in the illumination optical path instead of the diffractive optical element 6 in FIG. 1, a normal illumination light from a secondary light source arranged at 45 ° intervals around the optical axis AX is used. Quadrupole illumination can be performed.

  Further, by retracting the diffractive optical element 4 from the illumination optical path and setting a normal circular illumination diffractive optical element 63 in the illumination optical path instead of the diffractive optical element 6, normal circular illumination can be performed. . In this case, a light beam having a rectangular cross section enters the afocal zoom lens 5 along the optical ring AX. The light beam incident on the afocal zoom lens 5 is enlarged or reduced in accordance with the magnification, and is emitted from the afocal zoom lens 5 along the optical axis AX as a light beam having a rectangular cross section, and is incident on the diffractive optical element 63. Incident.

  Here, like the diffractive optical element 4, the diffractive optical element 63 for circular illumination has a function of forming a circular light intensity distribution in the far field when a parallel light beam having a rectangular cross section is incident. . Accordingly, the circular light beam formed by the diffractive optical element 63 forms a circular illumination field around the optical axis AX on the incident surface of the microlens array 8 via the zoom lens 7. As a result, a circular secondary light source centered on the optical axis AX is also formed on the rear focal plane of the microlens array 8. In this case, the outer diameter of the circular secondary light source can be changed as appropriate by changing the magnification of the afocal zoom lens 5 or the focal length of the zoom lens 7.

  The diffractive optical elements 6 and 60 to 63 in FIG. 1 are fixed on the circumference of a turret plate (not shown) rotated by the drive motor 13, for example, at equal angular intervals, and the drive motor 13 uses the turret plate. By rotating, a desired diffractive optical element can be installed on the illumination optical path. The drive motor 13 is controlled by the drive system 12 based on a command from the main control system 11 that controls the overall operation of the apparatus.

  Next, FIG. 4 is a diagram schematically showing the configuration of the phase member and the depolarizer of FIG. Referring to FIG. 4, the phase member 10 is composed of a half-wave plate in which the crystal optical axis is rotatable about the optical axis AX. On the other hand, the depolarizer 20 includes a wedge-shaped quartz prism 20a and a wedge-shaped quartz prism 20b having a shape complementary to the quartz prism 20a. The quartz prism 20a and the quartz prism 20b are configured to be detachable with respect to the illumination optical path as an integral prism assembly. When an ArF excimer laser light source (or KrF excimer laser light source) is used as the laser light source 1 as in this example, the degree of polarization of light emitted from the light source is typically 95% or more. Therefore, substantially linearly polarized light is incident on the half-wave plate 10.

  When the crystal optical axis of the half-wave plate 10 is set to make an angle of 0 ° or 90 ° with respect to the plane of polarization of the linearly polarized light incident thereon, the light of the linearly polarized light incident on the half-wave plate 10 Passes through without changing the plane of polarization. In addition, when the crystal optical axis of the half-wave plate 10 is set to form an angle of 45 ° with respect to the plane of polarization of the linearly polarized light incident thereon, the linearly polarized light incident on the half-wave plate 10 is The light is converted into linearly polarized light whose polarization plane is changed by 90 °. Further, when the crystal optical axis of the crystal prism 20a is set to make an angle of 45 ° with respect to the plane of polarization of the linearly polarized light that is incident, the linearly polarized light incident on the crystal prism 20a is converted into unpolarized light. Converted (unpolarized).

  In the present embodiment, when the depolarizer 20 is positioned in the illumination optical path, the crystal optical axis of the crystal prism 20a is configured to form an angle of 45 ° with respect to the polarization plane of the linearly polarized light incident thereon. . Incidentally, when the crystal optical axis of the crystal prism 20a is set to make an angle of 0 ° or 90 ° with respect to the plane of polarization of the linearly polarized light incident thereon, the linearly polarized light incident on the crystal prism 20a is polarized. The plane passes without changing. In addition, when the crystal optical axis of the half-wave plate 10 is set to make an angle of 22.5 ° with respect to the plane of polarization of the linearly polarized light that is incident, The light is converted into non-polarized light including a linearly polarized light component that passes through without changing its polarization plane and a linearly polarized light component whose polarization plane changes by 90 °.

  In the present embodiment, as described above, linearly polarized light from the laser light source 1 is incident on the half-wave plate 10. However, in order to simplify the following description, P-polarized light (in FIG. It is assumed that light of linearly polarized light polarized in the Z direction at the position of the two-wave plate 10 (hereinafter referred to as “Z-direction polarized light”) is incident on the half-wave plate 10. When the depolarizer 20 is positioned in the illumination optical path, the crystal optical axis of the half-wave plate 10 is set to make an angle of 0 ° or 90 ° with respect to the polarization plane of P-polarized light (Z-direction polarized light) incident thereon. The P-polarized light (Z-direction polarized light) incident on the half-wave plate 10 passes through the P-polarized light (Z-direction polarized light) without changing the polarization plane and enters the quartz prism 20a. Since the crystal optical axis of the quartz prism 20a is set to make an angle of 45 ° with respect to the polarization plane of the incident P-polarized light (Z-polarized light), the P-polarized light (Z-polarized light) incident on the quartz prism 20a. Is converted to light in an unpolarized state.

  The light depolarized through the quartz prism 20a illuminates the mask M (and thus the wafer W) in a non-polarized state through the quartz prism 20b as a compensator for compensating the traveling direction of the light. On the other hand, when the crystal optical axis of the half-wave plate 10 is set to form an angle of 45 ° with respect to the polarization plane of the P-polarized light (Z-direction polarized light) incident thereon, the P-polarized light incident on the half-wave plate 10. The polarization plane of the (Z-polarized) light changes by 90 ° and is S-polarized (linearly polarized in the X direction at the position of the half-wave plate 10 in FIG. 1 and hereinafter referred to as “X-directional polarized light”). ) And enters the quartz prism 20a. Since the crystal optical axis of the quartz prism 20a is set to make an angle of 45 ° with respect to the polarization plane of incident S-polarized light (X-direction polarized light), S-polarized light (X-direction polarized light) incident on the quartz prism 20a is set. ) Is converted into non-polarized light and illuminates the microlens array 8 and thus the mask M in the non-polarized state via the quartz prism 20b.

  On the other hand, when the depolarizer 20 is retracted from the illumination optical path, the crystal optical axis of the half-wave plate 10 forms an angle of 0 ° or 90 ° with respect to the polarization direction of the P-polarized light (Z-direction polarized light) incident thereon. With this setting, the P-polarized light (Z-direction polarized light) incident on the half-wave plate 10 passes through the P-polarized light (Z-direction polarized light) without changing the polarization plane, and the P-polarized light (Z-direction polarized light). The microlens array 8 is illuminated with the state light. On the other hand, when the crystal optical axis of the half-wave plate 10 is set to make an angle of 45 ° with respect to the polarization direction of the P-polarized light (Z-direction polarized light) incident thereon, the P-polarized light incident on the half-wave plate 10 The polarization plane changes by 90 ° to become S-polarized light, and the microlens array 8 is illuminated with light in the S-polarized (X-direction polarized) state.

  As described above, in this embodiment, the microlens array 8 (and thus the mask M) can be illuminated in a non-polarized state by inserting the depolarizer 20 into the illumination optical path and positioning it. Further, the depolarizer 20 is retracted from the illumination optical path and set so as to form an angle of 0 ° or 90 ° with respect to the polarization direction of the P-polarized light (Z-direction polarized light) on which the crystal optical axis of the half-wave plate 10 is incident. Thus, the microlens array 8 can be illuminated in the P-polarized (Z-direction polarized) state. Further, the depolarizer 20 is retracted from the illumination optical path, and the crystal optical axis of the half-wave plate 10 is set to be 45 ° with respect to the polarization direction of the P-polarized light (Z-polarized light) incident thereon. The microlens array 8 can be illuminated in a polarized state (X direction polarized light).

  Further, on the illumination optical path of the illumination system pupil plane PIL that is the rear focal plane of the microlens array 8 of this example, a polarization distribution setting plate 14 is detachably disposed along the slider 15 by a drive motor 16. Yes. The drive motor 16 is also controlled by the drive system 12 based on a command from the main control system 11. A polarization state control system is constituted by the polarization distribution setting plate 14, the slider 15, the drive motor 16, and the drive system 12. The polarization state control system (12, 14 to 16), the diffractive optical elements 6, 60 to 63, and the drive. The motor 13 constitutes an illumination condition control system.

  FIG. 2A shows the polarization distribution setting plate 14 on the illumination system pupil plane PIL. In FIG. 2A, the disk-shaped polarization distribution setting plate 14 includes the outer secondary light sources 23A and 23B. An annular half-wave plate 14A for covering and a circular half-wave plate 14B for covering inner secondary light sources 23C and 23D are connected to each other. In this case, the optical crystal axis 17A of the outer half-wave plate 14A is parallel to the Z-axis, and the optical crystal axis 17B of the inner half-wave plate 14B is inclined by 45 ° with respect to the Z-axis.

  In the state where the polarization distribution setting plate 14 is installed on the illumination optical path of the illumination system pupil plane PIL, the depolarizer 20 of FIG. 1 is retracted from the illumination optical path, and the rotation angle of the half-wave plate 10 is emitted. The polarization direction of the illumination light is set to be the Z direction. As a result, in FIG. 2A, the polarization direction of the linearly polarized illumination light that has passed through the outer half-wave plate 14A is the D1 direction parallel to the Z axis and passes through the inner half-wave plate 14B. The polarization direction of the linearly polarized illumination light is the D2 direction parallel to the X axis. That is, in the quadrupole illumination using the quadrupole secondary light sources 23A to 23D arranged in a line in the X direction, the polarization state of the illumination light from the pair of outer secondary light sources 23A and 23B is Z direction (straight line The polarization state of illumination light from the inner pair of secondary light sources 23C and 23D is linear polarization polarized in the X direction (direction parallel to the straight line 25A). is there.

  Further, in the quadrupole illumination using the secondary light sources 24A to 24D arranged in a line in the Z direction in FIG. 2B, the depolarizer 20 in FIG. Is set so that the polarization direction of the emitted illumination light is in the X direction. As a result, the polarization state of the illumination light from the outer pair of secondary light sources 24A and 24B is linearly polarized light polarized in the X direction (direction orthogonal to the straight line 25B), and the inner pair of secondary light sources 24C. The polarization state of the illumination light from 24D is linearly polarized light polarized in the Z direction (direction parallel to the straight line 25B). As a polarization distribution setting device, in addition to the above-described polarization distribution setting plate 14 in which a plurality of half-wave plates are combined, other mechanisms such as a mechanism using a polarizing plate and a mechanism using a plurality of independent light sources are used. A mechanism may be used.

Next, an example of an operation when transferring a plurality of contact hole patterns arranged in a lattice pattern onto the wafer W in FIG. 1 using the exposure apparatus of this example will be described.
FIGS. 6A and 6B are enlarged views of a part of the contact hole pattern exposed in this example. These patterns are formed, for example, in a part of the pattern formation region of the mask M in FIG.

  An X-direction dense pattern 32X as a contact hole pattern periodically arranged in the X direction in FIG. 6A has a transmittance of 6% with a width a in the X direction and a width c in the Y direction with the light shielding portion as a background. The halftone rectangular opening patterns 31 are arranged in the X direction at a pitch b. That is, the X-direction dense pattern 32X is a periodic pattern that is isolated in the Y direction and pitch b in the X direction. In this case, the X direction and the Y direction on the mask M correspond to the X direction and the Z direction on the illumination system pupil plane PIL (for example, FIG. 2A), respectively.

  As an example, the width a is 75 nm, the width c is 150 nm, and the pitch b is 150 nm when projected onto the wafer via the projection optical system PL of FIG. Even when a plurality of X-direction dense patterns similar to the X-direction dense pattern 32X are arranged at a pitch several times the pitch b in the Y direction with respect to the X-direction dense pattern 32X in FIG. Each X-direction dense pattern can be regarded as a unidirectional dense pattern isolated in the Y direction. When transferring the dense X-direction pattern 32X, the secondary light sources 23A to 23D arranged in a line in the X direction in FIG. 2A are used to show the polarization states from the secondary light sources 23A to 23D. A row of quadrupole illumination set as in 2 (A) is used.

  6B is a pattern obtained by rotating the X direction dense pattern 32X of FIG. 6A by 90 °. That is, the Y-direction dense pattern 32Y is a periodic pattern that is isolated in the X direction and pitch b in the Y direction. When the Y-direction dense pattern 32Y is transferred, the secondary light sources 24A to 24D arranged in a row in the Z direction in FIG. 2B are used to show the polarization states from the secondary light sources 24A to 24D. One row of quadrupole illumination set as 2 (B) is used.

  Next, when the X-direction dense pattern 32X arranged in a lattice pattern in FIG. 6A is exposed and transferred to each shot area on the wafer W via the projection optical system PL in FIG. The diffractive optical element 60 is disposed instead of the diffractive optical element 6. As a result, secondary light sources 23A to 23D having one row and four poles in the X direction in FIG. 2A are formed on the illumination system pupil plane PIL. This setting is performed by the main control system 11 according to the type of mask pattern to be exposed.

  Next, as a second stage, the main control system 11 arranges the polarization distribution setting plate 14 on the illumination system pupil plane PIL via the drive system 12 and changes the polarization state of the incident illumination light to the Z direction polarization. As a result, as shown in FIG. 2A, the polarization state of the illumination light emitted from the outer secondary light sources 23A and 23B is linearly polarized in the Z direction and is emitted from the inner secondary light sources 23C and 23D. The polarization state of the illumination light is linearly polarized in the X direction.

  Under the above conditions, the X-direction dense pattern 32X in FIG. 6A is projected onto each shot area on the wafer W via the projection optical system PL in FIG. As a result, the resolution and depth of focus of the image in the X direction (period direction) of the X direction dense pattern 32X are improved by the illumination light mainly from the two outer secondary light sources 23A and 23B in FIG. Further, the resolution and depth of focus of the image in the Y direction (isolation direction) of the X-direction dense pattern 32X are improved mainly by the illumination light from the two inner secondary light sources 23C and 23D. Further, since the illumination light from the two outer secondary light sources 23A and 23B is polarized in the Z direction (Y direction in FIG. 6A), the illumination light in the image of each aperture pattern 31 is directed in the Y direction. It becomes linearly polarized light, and the resolution of the image of each aperture pattern 31 is improved. Further, since the illumination light from the two inner secondary light sources 23C and 23D is polarized in the X direction, the X direction dense pattern 32X in FIG. 6A is regarded as an isolated line pattern extending in the X direction. Since the polarization direction of the illumination light is a direction along the isolated line, the resolution as an isolated line pattern is improved.

The illumination light from the outer secondary light sources 23A and 23B and the illumination light from the inner secondary light sources 23C and 23D have orthogonal polarization directions, and the light amounts of both are substantially simply added on the wafer surface. Thus, the resolution and depth of focus expansion effects in the periodic direction (X direction) and the isolated direction (Y direction) are not canceled out, and the resolution and depth of focus are improved as a whole.
On the other hand, when the Y-direction dense pattern 32Y arranged in a grid pattern in FIG. 6B is exposed and transferred to each shot area on the wafer W via the projection optical system PL in FIG. The diffractive optical element 61 is disposed in place of the diffractive optical element 6. As a result, secondary light sources 24A to 24D having four lines in a row in the Z direction in FIG. 2B are formed on the illumination system pupil plane PIL. Next, as a second stage, the polarization distribution setting plate 14 is arranged on the illumination system pupil plane PIL, and the polarization state of the incident illumination light is changed to the X direction polarization. As a result, as shown in FIG. 2B, the polarization state of the illumination light emitted from the outer secondary light sources 24A and 24B is linearly polarized in the X direction, and is emitted from the inner secondary light sources 24C and 24D. The polarization state of the illumination light is linearly polarized in the Z direction.

  Under the above conditions, the image of the Y-direction dense pattern 32Y in FIG. 6B is projected onto each shot area on the wafer W via the projection optical system PL in FIG. As a result, the resolution and depth of focus of the image in the Y direction (period direction) of the Y-direction dense pattern 32Y are improved by the illumination light mainly from the two outer secondary light sources 24A and 24B in FIG. Further, the resolution and depth of focus of the image in the X direction (isolation direction) of the Y-direction dense pattern 32Y are improved mainly by the illumination light from the two inner secondary light sources 24C and 24D.

  Next, FIGS. 7A and 7B are the same as those in FIG. 6A under the illumination condition in which the polarization state is controlled by using the one-row, four-pole secondary light sources 23A to 23D in FIG. The relationship between the exposure amount error (dose error) and the depth of focus (DOF) of the projection optical system PL when an image of the X direction dense pattern 32X is exposed through the projection optical system PL was obtained by computer simulation. Results are shown.

  For comparison, as shown in FIG. 5, when using secondary light sources 23 </ b> A to 23 </ b> D having one row and four poles as in FIG. 2A, illumination light emitted from the secondary light sources 23 </ b> A to 23 </ b> D A simulation was also performed for the case where the polarization directions were all in the Z direction (D1 direction). The exposure wavelength λ is 193.3 nm (ArF excimer laser), the numerical aperture NA on the image side of the projection optical system PL is 0.85, and the projection magnification is 1/4. Further, in FIG. 3, in terms of σ value, the numerical aperture NAi (radius of the circumference 27) of the illumination optical system is 0.90, and the distance R3 from the optical axes of the two inner secondary light sources 23C and 23D is 0.00. 25. The radius R2 of the secondary light sources 23C and 23D was set to 0.12.

Further, assuming that the mask pattern error is ± 1 nm on the wafer and the allowable dose error width is 6%, the allowable line width (critical dimension CD) of each opening pattern 31 in FIG. 6A is transferred. The error ΔCD is ± 10%.
FIG. 7A shows a simulation result in the case of using quadrupole illumination in which the polarization directions in FIG. 5 are all Z directions, and FIG. 7B shows the polarization direction in which the outer polarization direction in FIG. 7 shows simulation results in the case of using quadrupole illumination in the X direction, the horizontal axis of FIGS. 7A and 7B is the defocus (nm) of the wafer surface from the best focus position, and the vertical axis is The natural logarithm ln (E / E ₀ ) is a value obtained by dividing the exposure amount E giving an error by the appropriate exposure amount E ₀ . Also, curves 33A and 33B in FIG. 7A show simulation results in which the line width errors of the projected image are −10% and + 10%, respectively, and curves 34A and 34B in FIG. 7B are the lines of the projected image, respectively. The simulation results in which the width error is −10% and + 10% are shown.

  In FIG. 7A, the depth of focus DOF1, which is the width of the defocus amount in the range 33C where the dose error is within 6%, is 67 nm. In FIG. 7B, the range 34C where the dose error is within 6%. The depth of focus DOF2, which is the width of the defocus amount, is 184 nm. Therefore, in contrast to the comparative example of FIG. 5 (FIG. 7A), when a single row of quadrupole illumination in which the polarization directions are orthogonal to each other as shown in FIG. In B)), it is understood that the depth of focus is greatly improved by about 3 times when the one-way dense pattern is exposed.

  When the pattern to be exposed is, for example, a line and space pattern (hereinafter referred to as “L & S pattern”) arranged at a predetermined pitch in the X direction, for example, in FIG. In the case of a pattern elongated in the direction, bipolar illumination in the X direction in which the light amount distribution on the illumination system pupil plane PIL in FIG. 1 is as shown in FIG. 8A may be used. In the following FIGS. 8A and 8B and FIGS. 9A and 9B, portions corresponding to FIGS. 2A and 2B are denoted by the same reference numerals. 8A, 8B and 9A, 9B, the straight lines 25A, 25B and the straight lines 25C, 25D are virtual straight lines for explaining the arrangement of the secondary light sources, respectively. The circumference 27 is a circumference having the maximum numerical aperture NAi of the illumination optical system as a radius.

  In the illumination system pupil plane PIL of FIG. 8A, two Z directions (on the mask) are arranged symmetrically so as to sandwich the optical axis AX in the X direction and substantially inscribed to the circumference 27 of the numerical aperture NAi. The light amount of illumination light is set to be large in the elongated elliptical secondary light sources 23A and 23B in the direction corresponding to the Y direction), and the light amount of illumination light is set to almost zero in the other regions. When the pattern to be transferred is an L & S pattern arranged in the Y direction (in FIG. 6B, each opening pattern 31 is an elongated pattern in the X direction), the light amount distribution in FIG. Dipolar illumination in the Z direction rotated 90 ° is used.

  Using the dipole illumination of FIG. 8A, the exposure wavelength is 193 nm, the numerical aperture NA on the image side of the projection optical system PL is 0.92, and the σ value of the numerical aperture NAi of the illumination optical system is 0.97. Depth of focus was simulated when the line width of the L & S pattern to be transferred on the wafer was 60 nm and the pitch was 120 nm. As a result, the depth of focus was approximately 300 nm when the dose error was 4%.

  Further, in the dipole illumination of FIG. 8A, the depth of focus is similarly simulated using the polarization state of the illumination light as linearly polarized light polarized in the D1 direction parallel to the Z axis in the two secondary light sources 23A and 23B. It was. As a result, it was found that the depth of focus when the dose error was 4% was approximately 400 nm, and the depth of focus was improved by approximately 30% by using the polarization state control together.

Next, when a mask pattern in which a memory cell pattern and a peripheral circuit pattern are mixed is transferred by one exposure, the light amount distribution on the illumination system pupil plane PIL in FIG. 1 is as shown in FIG. Alternatively, quadrupole illumination in the X direction and the Z direction may be used.
In the illumination system pupil plane PIL of FIG. 8B, the optical axis AX is symmetrically sandwiched between the X direction and the Z direction, and is elongated in a pair of Z directions so as to be substantially inscribed in the circumference 27 of the numerical aperture NAi. Elliptical secondary light sources 23A and 23B and a pair of elliptical secondary light sources 24A and 24B elongated in the X direction are set. In the secondary light sources 23A, 23B, 24A, and 24B, the amount of illumination light is set large, and in other regions, the amount of illumination light is set to almost zero. By using this quadrupole illumination, a pattern arranged in any direction of the X direction and the Y direction on the mask can be transferred onto the wafer with a necessary resolution and a sufficient depth of focus.

  Also in this quadrupole illumination, control of the polarization state of illumination light may be used in combination. In this case, in FIG. 8B, the polarization state of the illumination light is separated in the Z direction as linearly polarized light polarized in the D1 direction parallel to the Z axis in the two secondary light sources 23A and 23B separated in the X direction. The two secondary light sources 24A and 24B are linearly polarized light polarized in the D2 direction parallel to the X axis. Thus, by using linearly polarized light substantially polarized in the circumferential direction with quadrupole illumination, the depth of focus can be improved.

Further, when the X direction dense pattern 32X in FIG. 6A is exposed, tripolar illumination in the X direction in which the light amount distribution on the illumination system pupil plane PIL in FIG. 1 is as shown in FIG. 9A is used. Also good.
On the illumination system pupil plane PIL in FIG. 9A, an elliptical secondary elongated in two Z directions (directions corresponding to the Y direction on the mask) arranged symmetrically so as to sandwich the optical axis AX in the X direction. The light amount of the illumination light is set to be large in the light sources 23A and 23B and the small annular light source 41 arranged on the optical axis AX, and the light amount of the illumination light is set to almost zero in other regions. When the pattern to be transferred is the Y-direction dense pattern 32Y in FIG. 6B, tripolar illumination in the Z direction obtained by rotating the light amount distribution in FIG. 9A by 90 ° is used.

When the tripolar illumination in FIG. 9A is used, the resolution and the depth of focus in the X direction, which is the periodic direction, are improved by the illumination light from the outer two secondary light sources 23A and 23B, and the center annular secondary The illumination light from the light source 41 improves the resolution and depth of focus in the Y direction, which is an isolated direction.
Furthermore, in the tripolar illumination in FIG. 9A, the polarization state control of the polarization state of the illumination light to linearly polarized light that is polarized in the D1 direction parallel to the Z axis may be used in combination. This further improves the depth of focus.

For example, when transferring the pattern of the peripheral circuit of the memory cell, nine-pole illumination in which the light amount distribution on the illumination system pupil plane PIL in FIG. 1 is as shown in FIG. 9B may be used.
In the illumination system pupil plane PIL of FIG. 9B, a large annular secondary light source 42 on the optical axis AX, four circular secondary light sources 43 surrounding the secondary light source 42, and four circular secondary light sources surrounding it. The light intensity of the illumination light is set to be large in the nine areas composed of the secondary light sources 44, and the light intensity of the illumination light is set to almost zero in the other areas. Also, five secondary light sources are arranged along the straight lines 25C and 25D, respectively, using a straight line 25C that intersects the X axis at + 45 ° and a straight line 25D that intersects at −45 °.

  In this case, the resolution and depth of focus of the isolated pattern are improved by the illumination light from the central secondary light source 42, and the medium pitch L & S pattern is improved by the illumination light from the four secondary light sources 43 surrounding it. The resolution and the depth of focus are improved, and the resolution and depth of focus of the fine pitch L & S pattern are improved by the illumination light from the four secondary light sources 44 surrounding the resolution and the depth of focus. Therefore, by using the 9-pole illumination shown in FIG. 9B, it is possible to expose peripheral circuit patterns including various patterns with high resolution and a deep focal depth.

  When illumination using the secondary light source shown in FIGS. 8A and 8B or FIGS. 9A and 9B is performed, the secondary light source corresponding to the diffractive optical element 6 in FIG. 1 is generated. To be replaced with another diffractive optical element. Thereafter, when illumination using the secondary light source of FIG. 8A, FIG. 8B or FIG. 9A is performed, the rotation angle of the half-wave plate 10 is further controlled and the depolarizer 20 is retracted from the illumination optical path. , And polarization control including exchange of the polarization distribution setting plate 14 with another polarization distribution setting plate. That is, in the exposure apparatus of FIG. 1, a plurality of illumination methods using the secondary light sources of FIGS. 2 (A), (B), FIGS. 8 (A), (B), and FIGS. 9 (A), 9 (B). Any lighting method selected from can be used.

  2A (FIG. 3), FIG. 2 (B), FIG. 8 (A), (B), and FIG. 9 (A), the outer secondary light sources 23A, 23B, 24A, 24B , Each of which is preferably an elongated ellipse, but may be other shapes such as a circle. Further, the outer secondary light sources 23A and 23B (or 24A and 24B) and the inner secondary light sources 23C and 23D (or 24C and 24D) in FIG. 2A (FIG. 3) (or FIG. 2B). And the intensity of illumination light does not necessarily have to be substantially the same.

Next, a second embodiment of the present invention will be described with reference to FIGS. In this example as well, the exposure apparatus shown in FIG. 1 is basically used. In this example, in addition to the operation of the above-described embodiment, the image of the mask pattern by the projection optical system PL and the wafer surface are further relatively moved (or relatively vibrated) in the optical axis direction of the projection optical system PL during exposure.
FIG. 10 shows the main part of the wafer stage system of the exposure apparatus of FIG. 1. In FIG. 10, the wafer W is sucked and held on the Z leveling stage 35, and the Z leveling stage 35 is placed in three Z directions. It is supported on an XY stage 37 via drivable actuators 36A, 36B, and 36C. The XY stage 37 is driven on the wafer base 39 in the X and Y directions by a drive mechanism including a linear motor (not shown). . A wafer stage 38 that includes a Z leveling stage 35, actuators 36 </ b> A to 36 </ b> C, and an XY stage 37 and holds the wafer W (a moving device that relatively moves the mask pattern image and the wafer W in the optical axis direction of the projection optical system PL). Is configured.

  In this case, an optical oblique incidence type focus position detection system (not shown) for measuring the focus position (position in the optical axis AX1 direction) of the surface of the wafer W is disposed near the side surface of the projection optical system PL. The focus position of the wafer W can be controlled even during exposure by controlling the drive amount in the Z direction of the actuators 36A to 36C based on the detection result of the focus position detection system. Thereby, the image of the pattern of the mask M by the projection optical system PL and the wafer surface are relatively moved in the direction of the optical axis AX1 during the exposure. That is, the relative positional relationship of the wafer surface with respect to the image plane changes continuously or stepwise within the depth of focus of the projection optical system PL during exposure, and a predetermined area of the wafer surface to be exposed has different focus positions. Each shot is irradiated with illumination light. Instead of moving the wafer surface in the Z direction or in combination with it, the projection optical system PL is moved by, for example, moving the mask surface in the Z direction or moving at least one optical element of the projection optical system PL. Obviously, the image plane (pattern plane) of the image may be moved.

  In this example, the X direction dense pattern 32X in FIG. 6A (or FIG. 6B) is used by using a single row of quadrupole illumination in which the polarization directions in FIG. 2A (or FIG. 2B) are orthogonal. When exposing a one-way dense pattern such as the Y-direction dense pattern 32Y), the wafer W is moved by ΔZ along the optical axis AX1 of the projection optical system PL as shown in FIG. The movement width ΔZ is smaller than the thickness of the photoresist on the wafer W and is about the width of the focal depth of the projection optical system PL or smaller.

  FIGS. 11A and 11B respectively show an exposure error (dose error) and a depth of focus when the wafer surface is stationary in the optical axis direction during exposure and when the wafer surface is moved in the optical axis direction. An example of the simulation result which calculated | required the relationship with (DOF) is shown, the horizontal axis of FIG. 11 (A) and (B) is a dose error (%), and a vertical axis | shaft is a depth of focus (DOF). The mask pattern and illumination conditions are the same as in the case of FIG. In FIGS. 11A and 11B, the depth of focus DOFa is an example of a practical lower limit value of the depth of focus, and the dose error ΔE is an example of a lower limit value of which the dose error can be controlled.

  A curve 40A in FIG. 11A shows a relationship between a dose error and a depth of focus when the X-direction dense pattern 32X in FIG. 6A is exposed with, for example, normal dipole illumination, and a curve 40B is shown in FIG. For example, the relationship between the dose error and the depth of focus when the X-direction dense pattern 32X in FIG. 6A is exposed using a line of quadrupole illumination in which the polarization directions in FIG. 2A are orthogonal to each other is shown. As described above, when the depth of focus does not reach the practical lower limit DOFa even when using a single row of quadrupole illumination in FIG. 2A, it is desirable to use the operation of moving the wafer surface in the optical axis direction.

  11B, curves 40A and 40B are the same as those in FIG. 11A, and curve 40C is obtained by using, for example, a row of quadrupole illumination in which the polarization directions are orthogonal to each other in FIG. FIG. 10 shows the relationship between the dose error and the depth of focus when the wafer surface is moved by a predetermined width in the direction of the optical axis AX1 as shown in FIG. The relationship between the dose error and the depth of focus when the movement width of the wafer surface in the direction of the optical axis AX1 is made wider than in the case of the curve 40C is shown.

  From FIG. 11 (A), by using a single row of quadrupole illumination in which the polarization directions in FIG. 2 (A) (or FIG. 2 (B) are orthogonal), the tolerance of the dose error and the tolerance of the depth of focus can be reduced. You can see that both can be expanded. In addition, from FIG. 11B, by combining the operation of moving the wafer surface in the optical axis direction, the allowable range of the depth of focus can be further expanded, and the amount of movement of the wafer surface can be widened to increase the depth of focus. It can be seen that the amount of expansion of the allowable range also increases.

As described above, according to this example, the projection optics between the mask pattern image and the wafer surface during exposure with respect to the row of quadrupole illumination in which the polarization directions in FIG. 2A or FIG. By performing the relative movement of the system PL in the optical axis direction, the depth of focus when the one-way dense pattern is exposed can be further increased.
In the above embodiment, the pattern to be transferred is a contact hole pattern, but the pattern is a pattern provided in a semiconductor device such as a flash memory (SRAM or the like) or a CPU, for example. However, in the above embodiment, the pattern to be transferred may be any other pattern arranged in a one-dimensional or two-dimensional lattice.

  In the exposure apparatus of the above-described embodiment, after installing a column mechanism (not shown), an illumination optical system composed of a plurality of lenses and a projection optical system composed of a catadioptric system are incorporated in the exposure apparatus body and optical adjustment is performed. Then, a reticle stage or wafer stage made up of a large number of mechanical parts can be attached to the exposure apparatus body, wiring and piping are connected, and overall adjustment (electrical adjustment, operation check, etc.) can be made. The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  Further, when a semiconductor device is manufactured using the exposure apparatus of the above-described embodiment, the semiconductor device includes a step of designing a function and performance of the device, a step of manufacturing a reticle based on this step, and a wafer from a silicon material. Forming step, aligning with the exposure apparatus of the above-described embodiment to expose the pattern of the reticle onto the wafer, forming circuit pattern such as etching, device assembly step (including dicing process, bonding process, and packaging process) ) And an inspection step. This semiconductor device preferably includes at least a flash memory (such as SRAM) and a CPU.

The present invention can also be applied to the case where exposure is performed with an immersion type exposure apparatus disclosed in, for example, International Publication No. 99/49504. The present invention can also be applied to the case where exposure is performed with a projection exposure apparatus that uses extreme ultraviolet light (EUV light) having a wavelength of about several nm to 100 nm as an exposure beam.
In addition, the present invention is not limited to application to an exposure apparatus for manufacturing a semiconductor device, for example, an exposure apparatus for a display device such as a liquid crystal display element formed on a square glass plate or a plasma display, It can also be widely applied to an exposure apparatus for manufacturing various devices such as an image sensor (CCD or the like), a micromachine, a thin film magnetic head, and a DNA chip. Furthermore, the present invention can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithographic process.

  In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.

  According to the present invention, when transferring a plurality of patterns arranged in a one-way dense lattice, a high resolution can be obtained and a wide depth of focus can be secured. Therefore, for example, a device including a contact hole can be manufactured with high yield and high accuracy.

It is a figure which shows the exposure apparatus used in the 1st Embodiment of this invention. (A) is a figure which shows secondary light source 23A-23D of 1 row 4 poles in the X direction on the illumination system pupil plane PIL of FIG. 1, (B) is 2 rows of 4 poles in a row on the Z direction on the illumination system pupil plane PIL. It is a figure which shows next light sources 24A-24D. It is a figure which shows the detailed arrangement | positioning of secondary light source 23A-23D of FIG. 2 (A). It is a figure which shows the one part optical member which controls the polarization state in FIG. It is a figure which shows the state which made the polarization direction of illumination light the same direction in secondary light source 23A-23D of 1 row 4 poles of FIG. 2 (A). (A) is an enlarged view showing an X direction dense pattern 32X to be transferred, and (B) is an enlarged view showing a Y direction dense pattern 32Y to be transferred. (A) is a figure which shows the simulation result of the imaging characteristic at the time of using the illumination of FIG. 5, (B) is a figure which shows the simulation result of the imaging characteristic at the time of using the illumination of FIG. 2 (A). . It is explanatory drawing of the other illumination method used by 1st Embodiment. It is explanatory drawing of another illumination method used in 1st Embodiment. It is a figure which shows the principal part of the wafer stage system of the exposure apparatus used in the 2nd Embodiment of this invention. (A) is a diagram showing a simulation result of imaging characteristics when the illumination of FIG. 2 (A) is used, and (B) is a simulation of imaging characteristics when the operation of moving the wafer surface of FIG. 10 is further used together. It is a figure which shows a result.

Explanation of symbols

  M ... Mask, PL ... Projection optical system, W ... Wafer, 6, 60-63 ... Diffractive optical element, 8 ... Micro lens array, 12 ... Drive system, 14 ... Polarization distribution setting plate, 23A-23D ... One row in X direction 4 poles secondary light source, 24A-24D ... 1 row 4 poles secondary light source in Z direction, 31 ... aperture pattern, 32X ... X direction dense pattern, 32Y ... Y direction dense pattern

Claims (12)

In an exposure method of transferring and exposing a plurality of patterns arranged in a lattice shape onto an object via a projection optical system,
When illuminating a plurality of the patterns with the exposure beam from the illumination optical system, two first regions that are substantially symmetrically shifted from the optical axis on the pupil plane of the illumination optical system, and inside the two first regions Increasing the amount of light of the exposure beam in the two second regions shifted substantially symmetrically with respect to the optical axis, compared to other regions;
Setting the polarization state of the exposure beam to linearly polarized light whose polarization direction is substantially orthogonal between the two first regions and the two second regions on the pupil plane of the illumination optical system. An exposure method characterized by the above.   A step of relatively moving the image of the pattern and the object in the optical axis direction of the projection optical system when projecting a plurality of patterns of images onto the object via the projection optical system; The exposure method according to claim 1. Each of the two first and second regions on the pupil plane of the illumination optical system are arranged along a straight line substantially passing through the optical axis;
The polarization direction of the exposure beam in the two first regions is a direction orthogonal to the straight line, and the polarization direction of the exposure beam in the two second regions is a direction parallel to the straight line. The exposure method according to claim 1 or 2.   The plurality of patterns are periodically arranged in a direction corresponding to a direction parallel to the straight line, and are substantially isolated in a direction corresponding to a direction orthogonal to the straight line. 4. The exposure method according to 3. The coherence factor outside the two first regions is 0.8 to 0.95;
The distance between the center of the two second regions and the optical axis is 0.15 to 0.35 in terms of a coherence factor, and the second region is 0.05 to 0.2 in terms of a coherence factor. The exposure method according to any one of claims 1 to 4, wherein the exposure method is a circular region having a radius of.   A device manufacturing method comprising an exposure step of transferring a circuit pattern onto a photoconductor using the exposure method according to claim 1.   The device manufacturing method according to claim 6, wherein the exposure step is a part of a contact hole forming step. In an exposure apparatus that illuminates a predetermined pattern with an exposure beam from an illumination optical system and exposes an object with an image through the projection optical system of the predetermined pattern,
When the predetermined pattern includes a plurality of patterns arranged in a lattice pattern,
According to the arrangement of the plurality of patterns, two first regions that are substantially symmetrically shifted from the optical axis on the pupil plane of the illumination optical system, and substantially within the two first regions with respect to the optical axis. While increasing the amount of light of the exposure beam in the two second regions that are symmetrically shifted from other regions,
An illumination condition control system for setting the polarization state of the exposure beam to linearly polarized light in which the polarization direction is substantially orthogonal between the two first regions and the two second regions on the pupil plane of the illumination optical system; An exposure apparatus comprising the exposure apparatus.   The exposure apparatus according to claim 8, further comprising a moving device that relatively moves the image of the predetermined pattern and the object in an optical axis direction of the projection optical system. Each of the two first regions and the second region on the pupil plane of the illumination optical system is substantially arranged along a straight line passing through the optical axis, and the illumination condition control system includes:
The polarization direction of the exposure beam in the two first regions is a direction orthogonal to the straight line, and the polarization direction of the exposure beam in the two second regions is a direction parallel to the straight line. Item 10. The exposure apparatus according to Item 8 or 9.   The plurality of patterns are periodically arranged in a direction corresponding to a direction parallel to the straight line, and are substantially isolated in a direction corresponding to a direction orthogonal to the straight line. The exposure apparatus according to 10.   The device manufacturing method characterized by including the exposure process which transfers a circuit pattern on a photoreceptor using the exposure apparatus as described in any one of Claims 8-11.

Images